Light sensitive, photothermographic film is used in many applications ranging from photocopying apparatus, to graphic arts and/or medical imaging/recording printing systems. For example, in the medical industry, laser imaging systems employing photothermographic film are commonly used to produce photographic images from digital image data generated by magnetic resonance (MR) computed tomography (CT) or other types of scanners. Systems of this type typically include a laser imager for exposing the image on the photothermographic film, a thermal film processor for developing the film through the application of heat, and an image management subsystem for coordinating the operation of the laser imager and the thermal film processor. The light sensitive photothermographic film can include a thin polymer or paper base coated with an emulsion of dry silver or other heat sensitive material.
One known type of thermal processor for use in developing the photothermographic film utilizes a thermal drum processor. Once the film has been subjected to photo stimulation by optical means, such as laser light, it is fed into the thermal drum processor for development.
The thermal drum processor includes a rotating drum cylinder which is heated to develop the film. For example, the drum surface may be heated utilizing a heating element coupled to the drum, or alternatively, other methods may be used such as the rotating drum cylinder being located within an oven-like enclosure.
The film is engaged by the rotating drum and heated at a desired rate or "dwell time" to allow for development of the images on the photothermographic film. Mechanisms may be employed for holding the film against the rotating drum surface, such as through the use of a plurality of rollers positioned about the drum surface or other means, such as by electrostatically charging the drum surface, or the use of belts. After development, the film is removed from the rotating drum and cooled.
After a number of thermal processing cycles, debris and film residue are left on the thermal processing drum and its associated parts. As the debris and film residue build up on the drum surface, the film has a tendency to stick to the drum surface, and may be reluctant to separate from the drum surface after thermal processing. When the film does not adequately release from the drum surface, a film jam is typically reported, resulting in removal by the operator and/or drum maintenance.
In one thermal processing system, a guide member is employed to guide the film as it releases from the rotating drum cylinder. The guide bar is formed of a rigid metal, such as aluminum. The guide bar is spaced longitudinally across the surface of the drum in a direction generally perpendicular to the rotation of the drum. The guide bar does not contact the drum surface, being spaced a small distance (e.g., 815/1000 of an inch) from the drum surface. During thermal processing, debris builds up on the drum surface and also condenses on the guide bar. As the gap between the guide bar and the drum surface becomes smaller, the guide bar may start to dig into the drum surface and may ultimately destroy the drum. Further, once the debris builds up on the drum surface, the film will jam requiring operator removal and/or drum maintenance and cleaning.